Vegetative Reproduction in Flowering Plants
Investigating Asexual Reproduction of Angiosperms
Sexual reproduction is a great scheme. It has been and continues to be so effective that seed plants dominant the earth numbering in the hundreds of thousands of species. However, if there is one thing that all life on this planet learned early on, it is that you must be adaptable to survive. And to be adaptable, you need more than one way of getting things done. Creatures limited to one plan are targets for extinction. So when it comes to reproduction in seed plants, what is Plan B? What other methods of reproduction can plants employ beside that of sexual union?
The answer lies within the vegetative body of the plant and is known appropriately as vegetative reproduction. This method of reproduction involves some part of the plant body – roots, shoots, or leaves – producing new plants. The advantage to this tactic as compared to sexual reproduction is that it can produce many individuals in a short period of time.
However, vegetatively-reproduced plants lack the genetic diversity of sexually reproduced plants as all the offspring are genetically identical to the original parent plant and to each other. Thus, the clones all have the same tolerance to environmental change and are attacked by the same diseases and pests, constantly under threat of total annihilation.
Shoots from Roots
The capacity to reproduce vegetatively is largely confined to herbaceous (soft stems) and woody (hard stems) perennials. The structures that make this type of reproduction possible are aerial stems known as stolons or runners, rhizomes (underground stems), and horizontal roots.
Aerial stems, where they touch the soil, send up shoots and produce roots at the nodes. The strawberry, many “weeds”, and a number of other plants vegetatively reproduce this way.
Reproduction by means of underground parts—roots or rhizomes—is even more common. Rhizomes also form auxiliary buds and roots at the nodes. The buds give rise to branches, and independent plants arise as the older parts die.
A number of ornamentals and weeds, such as lily of the valley, many mints, most perennial grasses, poison ivy, sweet flag, and wild morning-glory spread in this manner. Cattails and sedges, both spreading by rhizomes, often occupy great areas of marshland. Ferns may also spread by means of rhizomes.
An extremely rapid rate of vegetative reproduction is found in the water hyacinth, an attractive yet environmentally troublesome weed in many parts of the southern United States, which reproduces by rhizomes. It is estimated that 10 of these plants could produce 655,360 plants during a growing season of 8 months. These plants would cover an acre of water surface and be so thick as to block navigation by small water craft.
Also striking is the reproductive rate of our native blueberries. A species of blueberry native to the southeastern United States was found to annually produce new rhizomes averaging about a foot in length. A clone of this plant, radiating out from the center, covered an area a half a mile in diameter and was estimated to be 1,000 years old.
The formation of adventitious shoots from horizontal roots is also common. Shoots from roots occurs in the Canada thistle, bindweed, milkweed, and many other herbaceous weeds. Such stems also frequently arise from the horizontal roots of woody plants, such as Osage orange, sumac, beech, elderberry, and lilac. Thick groves or clumps of woody plants are often formed as a result of this method of reproduction.
Vegetative Reproduction is Important
Vegetative reproduction plays an important natural role. Many perennial plants, woody and herbaceous, are able to spread over wide areas because of vegetative multiplication. This ability enables grasses, for example, to become the dominant plants of meadow, prairie, and plains in many parts of the world.
The rapidity with which some plants spread by this method enables us to use perennial grasses, legumes, and other plants in the control of erosion on sloping lands, in gullies, and on sand dunes. The masses of roots and subterranean stems, along with the aerial parts of the plants, stabilize the soil against the destructive action of water and wind.
The capacity for vegetative reproduction also allows a partially destroyed plant to regenerate lost or damaged parts. For example, a portion of the tap root of a dandelion left in the soil following attempts to remove the plant by hand digging forms adventitious buds that shortly produce leaves above the soil line. Many hardwood forest trees, after cutting, produce sprouts from the stumps. In the replacement of the forest in cut-over areas, this type of reproduction may be more important than growth from seed. Adventitious shoots may arise not only from wound tissue on the stump but also from roots lying near the soil surface.
If sexual reproduction is plan A in the plant world, then vegetative (asexual) reproduction is surely plan B.
Banana Trees Will Sprout From Roots
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